This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
Rechargeable Li-ion batteries are integral part of modern portable electronic devices, medical implants, and electric vehicles. Their acceptability for a wide range of applications resulted from the increased energy density and high rate capabilities compared to other secondary batteries. Graphite is mostly used as the anode material for these rechargeable Li-ion batteries due to only 10% volume change during lithium intercalation into ordered graphitic planes, and improved electronic conductivity over alternative metal-oxide electrodes. Despite these advantages, the specific capacity of graphite is limited to 372 mAh/g, and high rate performances are not promising. These drawbacks of conventional graphite anodes seriously limit the energy and power density of Li-ion batteries. Moreover, lithiation occurs at lower potentials (<0.3 V vs Li+/Li), which results in possible short circuit and fire due to lithium dendrite growth.
Amorphous and hard carbons composed of disordered graphitic planes are promising alternatives to graphite anodes due to their improved specific capacity, and higher lithiation potential (offering improved safety). Such partially graphitic carbons can accommodate Li-ions in the disordered interlayers as well as in the micropores (micropores usually refer to pore sizes less than 2 nm) and offer excellent cycling stability and efficiency for rechargeable battery anodes. In addition, carbon nanomaterials such as nanoparticles, nanotubes, nanofibers, nanosheets, graphene, and fullerenes have also been used for Li-ion storage. Improved electrochemical performances of these 1-D and 2-D nanostructures resulted from the superior electronic and Li-ion diffusion due to their inimitable microstructure, high surface area, and porosity. However, these high surface area carbons experience severe capacity fading upon prolonged cycling due volume change during lithiation and extreme reactivity with acidic electrolyte. State of the art synthesis of these carbonaceous materials often involves the use of hydrocarbon precursors such as acetylene or coal. Complicated synthetic methods including chemical vapor deposition (CVD), electric arc discharge, and laser deposition are usually employed for the fabrication of carbon nanotubes and graphene. These complex methods that rely on hydrocarbon precursors could be commercially non-viable, environmentally non-benign and expensive.
Thus an unmet need exists for simple scalable and inexpensive synthetic methods for high capacity carbon electrodes for Li-ion batteries. Further it is desirable that such methods are relatively inexpensive and environmentally benign.